v3: generated placeholder thumbnails for pages with no preview image, and a fix for hotlink-protected ones

Thumbnails were failing in two different ways that both ended as an empty box.

Cloudflare hotlink protection answers a cross-site Referer with 403, so images
we had extracted correctly (dles.aukspot.com's og:image among them) never
rendered — every onError handler set display:none and swallowed it. The new
Thumbnail component loads with referrerPolicy="no-referrer", retries once
through /api/proxy-image for hosts that reject an empty referrer too, and only
then falls back to a placeholder.

Separately, the extraction cascade ended at the page's icon and then a guessed
/favicon.ico, so thumbnailUrl was almost never empty — just a 16x16 icon
cover-cropped into a 128x72 box. It now stops at real artwork, with faviconUrl
and accentColor (theme-color / msapplication-TileColor / mask-icon) as their own
fields. An absent thumbnailUrl finally means "no artwork", which is what makes
the placeholder possible: the site's own color mixed into the theme surface,
with its favicon centered on it, or its initial. Contrast holds for any
third-party color by construction rather than by luminance math, so nyt only
has to set --thumb-tint-strength to 0% to stay monochrome and geocities only
has to raise it. Missing accents fall back to a stable hostname-derived hue, so
rows saved before this get a tint with no backfill.

Migration 0011 reclassifies favicon-shaped thumbnailUrls on existing dumps.
The journal mosaic keeps its pull-quote and text fallbacks — the placeholder
appears there only to repair a broken image.

Also fixed: refresh silently overwrote good metadata with a failure stub, the
refresh button swallowed every error, refresh never broadcast the update,
extractBestIcon ranked SVG icons below 16x16 PNGs, and shared links with no
artwork carried no og:image at all.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/components/RichContentCard.tsx

@@ -1,21 +1,7 @@
 import { useContext } from "react";
 import type { RichContent } from "../model.ts";
 import { PlayerContext } from "../contexts/PlayerContext.ts";
-import { API_URL } from "../config/api.ts";
-
-/** Route HTTP thumbnail URLs through the server proxy to avoid mixed-content blocks. */
-function proxyIfHttp(url: string): string {
-  try {
-    const u = new URL(url);
-    if (
-      u.protocol === "http:" && u.hostname !== "localhost" &&
-      u.hostname !== "127.0.0.1"
-    ) {
-      return `${API_URL}/api/proxy-image?url=${encodeURIComponent(url)}`;
-    }
-  } catch { /* relative URL — leave as-is */ }
-  return url;
-}
+import Thumbnail from "./Thumbnail.tsx";
 
 interface RichContentCardProps {
   richContent: RichContent;
@@ -31,12 +17,26 @@ export default function RichContentCard(
     RichContentCardProps,
 ) {
   const { play, current, playing } = useContext(PlayerContext);
-  const thumbnailSrc = thumbnailOverrideUrl ??
-    (richContent.thumbnailUrl
-      ? proxyIfHttp(richContent.thumbnailUrl)
-      : undefined);
+  const thumbnailSrc = thumbnailOverrideUrl ?? richContent.thumbnailUrl;
+
+  const placeholder = {
+    url: richContent.url,
+    accentColor: richContent.accentColor,
+    faviconUrl: richContent.faviconUrl,
+    siteName: richContent.siteName,
+  };
 
   if (compact) {
+    const thumbnail = (
+      <Thumbnail
+        src={thumbnailSrc}
+        alt={richContent.title ?? ""}
+        className="rich-content-compact-thumbnail"
+        placeholder={placeholder}
+        placeholderClassName="rich-content-compact-thumbnail"
+      />
+    );
+
     if (richContent.embedUrl) {
       const isActive = current?.kind === "embed" &&
         current.embedUrl === richContent.embedUrl;
@@ -60,18 +60,7 @@ export default function RichContentCard(
           }}
           aria-label={isPlaying ? "Pause" : "Play"}
         >
-          {thumbnailSrc
-            ? (
-              <img
-                src={thumbnailSrc}
-                alt={richContent.title ?? ""}
-                className="rich-content-compact-thumbnail"
-                onError={(e) => {
-                  (e.target as HTMLImageElement).style.display = "none";
-                }}
-              />
-            )
-            : <span className="rich-content-compact-icon">▶</span>}
+          {thumbnail}
           <span className="rich-content-play-overlay">
             {isPlaying ? "⏸" : "▶"}
           </span>
@@ -87,63 +76,44 @@ export default function RichContentCard(
         className="rich-content-compact"
         onClick={(e) => e.stopPropagation()}
       >
-        {thumbnailSrc
-          ? (
-            <img
-              src={thumbnailSrc}
-              alt={richContent.title ?? ""}
-              className="rich-content-compact-thumbnail"
-              onError={(e) => {
-                (e.target as HTMLImageElement).style.display = "none";
-              }}
-            />
-          )
-          : <span className="rich-content-compact-icon">🔗</span>}
+        {thumbnail}
       </a>
     );
   }
 
   const canPlay = !!richContent.embedUrl;
 
-  const thumbnail = thumbnailSrc && (
-    canPlay
-      ? (
-        <button
-          type="button"
-          className="rich-content-thumbnail-btn"
-          onClick={() =>
-            play({
-              kind: "embed",
-              embedUrl: richContent.embedUrl!,
-              title: richContent.title,
-              type: richContent.type,
-              dumpHref,
-            })}
-          aria-label="Play"
-        >
-          <img
-            src={thumbnailSrc}
-            alt={richContent.title ?? ""}
-            className="rich-content-thumbnail"
-            onError={(e) => {
-              (e.target as HTMLImageElement).style.display = "none";
-            }}
-          />
-          <span className="rich-content-play-overlay">▶</span>
-        </button>
-      )
-      : (
-        <img
-          src={thumbnailSrc}
-          alt={richContent.title ?? ""}
-          className="rich-content-thumbnail"
-          onError={(e) => {
-            (e.target as HTMLImageElement).style.display = "none";
-          }}
-        />
-      )
+  const thumbnailImg = (
+    <Thumbnail
+      src={thumbnailSrc}
+      alt={richContent.title ?? ""}
+      className="rich-content-thumbnail"
+      placeholder={placeholder}
+      placeholderClassName="rich-content-thumbnail"
+    />
   );
 
+  const thumbnail = canPlay
+    ? (
+      <button
+        type="button"
+        className="rich-content-thumbnail-btn"
+        onClick={() =>
+          play({
+            kind: "embed",
+            embedUrl: richContent.embedUrl!,
+            title: richContent.title,
+            type: richContent.type,
+            dumpHref,
+          })}
+        aria-label="Play"
+      >
+        {thumbnailImg}
+        <span className="rich-content-play-overlay">▶</span>
+      </button>
+    )
+    : thumbnailImg;
+
   return (
     <div className={`rich-content-card rich-content-card--${richContent.type}`}>
       {thumbnail}